Windmill

ABSTRACT

Wind power plant with a wind turbine with a turbine shaft with which a generator shaft, which can be an extension of the turbine shaft, is connected to the rotor ( 12 ) of an electric generator. The rotor is radially surrounded by a stator, the turbine shaft is journalled in two bearing housings with bearings arranged on a base at the top of a tower, the base is pivotable around a vertical axis, and a motor is provided to effect the pivoting. The generator shaft is integrated with or rigidly connected to a flexing turbine shaft, the stator and rotor are carried by the generator shaft, to allow the generator to follow the flexing movement of the turbine shaft and the stator is locked against turning by a non-rotatable coupling which transfers substantially no bending moment or axial force acting against the flexing of the turbine shaft due to the bending moment acting on the turbine shaft from its hub, the bearings being provided to allow flexing of the turbine shaft.

The invention relates to a wind power plant according to theintroduction of claim 1.

PRIOR ART AND ITS WEAKNESSES

A major technical challenge in the design and development of wind powerplants, is to ensure that the bending moment acting on the turbine hubfrom the blades does not create damaging deformations in the remainingstructure. This relates particularly to deformations which may influencethe air gap between the rotor and the stator when the turbine shaftcarries an electric generator without any intermediate gearbox, ordeformations straining the wheels of the gearbox and reducing theservice life when a gearbox is used between the turbine shaft and thegenerator

It is known to provide having wind turbine powering a generator arrangedat the top of a column or tower. One solution is to connect the hub ofthe wind turbine directly to the rotor. The rotor is in turn carried bya base connected to the top of the tower, and the stator is carried bythe base without making any effort to coordinate the movements of therotor and the stator. Experience shows that this design does not givethe necessary control of the air gap between the rotor and the statorupon a bending moment strain being set up on the turbine shaft from thehub of the wind turbine. Also the generator can not be made ready foruse prior to mounting. Another solution is proposed in German PatentPublication 4402184 A1, wherein the hub of the wind turbine is connecteddirectly to the rotor of the generator without any connecting gearboxand wherein the rotor and the stator is connected through two bearingsproviding a coordinated movement. This solution allows for premountingof the generator as a complete unit in a factory, and testing prior tothe on site mounting.

Calculations shows that even this design will not provide a desirableconstant air cap, when the wind turbine exceeds a certain size in powerand weight, without making the dimensions of the supporting baseunecessary large.

It has also been proposed to arrange the generator on the opposite sideof the wind turbine relative to the top of the tower and connect thewind turbine to the generator over a turbine shaft between the hub andthe rotor of the generator—either in a rigid connection or over acoupling which transfers no bending moment, and without an intermediategearbox—and wherein the turbine shaft and the generator are journalledin a support arrangement with two or more bearings integrated in thesupport arrangement. The purpose of this arrangement is to reduce thebending acting on the part of the shaft adjoining the generator, byforcing the shaft through radial reaction forces from the bearing, backto the neutral position relative to the bending of the shaft withoutthis arrangment, to have a tight as possible air gap between the rotorand the stator. With this solution the bearings are subject to highbearing forces, and additionally the design requires a very rigid baseto accomodate the increased bearing.

OBJECT

The main object of the invention is to provide a wind power plantwherein the stator and the rotor during operation maintain their mutualdistance (air gap), independent on the deflection of the turbine shaftdue to the bending moment acting on the hub of the wind turbine in thecases where the turbine shaft is connected directly to the generator. Inthe embodiments wherein a gearbox is arranged between the turbine shaftand the generator, the invention should relieve the gearbox fromunexpected forces, which may reduce the service life relative to thenorm.

THE INVENTION

The present invention is described in patent claim 1. This can beembodied in different ways and designs, which are adaptable to varioussizes of wind turbines and different generator designs.

The present invention concerns the journalling of the turbine shaft in awind power plant powered by a wind turbine at one end of the shaft, andwherein an electric generator is connected to the shaft either outsiderelative to two bearing housings, or between a bearing housing facingthe wind turbine and a rear bearing housing, to reduce the effect of thebending moment acting on the shaft, due to forces acting on the hub ofthe wind turbine, on the air gap between the rotor and the stator of thegenerator, using a journalling according to patent claim 1.

This provides an advantageous combination of simple structure andfavourable journalling properties which contributes to keep the air gapbetween the rotor and the stator of the generator as small and constantas possible during the operation of the wind power plant, and withoutstraining the bearings excessively due to the forces created by thebending moment acting on the hub.

This enables a transfer of torque from the turbine shaft to the rotor,and from the rotor through the electrical field to the stator and via anon-rotatable coupling to one of or both bearing housings, or directlyto the base.

Further advantageous features are stated in claims 2-10.

When using a gearbox interposed between the turbine shaft and thegenerator, the invention allows for a direct attachment of input inshaft of the gearbox to the turbine shaft, which then carries thegearbox which in turn carries a generator base supporting the generator,and wherein the rotor of the generator is connected to the output shaftof the gearbox, with a rigid or elastic coupling. The transfer of torquefrom the rotor to the stator and from there to the base will also inthis case be carried out by the non-rotatable coupling which will bedescribed for the direct driven generator.

EXAMPLES

The invention is further described below with reference to the drawingswherein:

FIG. 1 shows a vertical section through an embodiment with a two-sidedjournalling of the stator on the shaft,

FIG. 2 shows a vertical section of a corresponding embodiment with asingle-sided journalling of the stator on the shaft,

FIG. 3 shows a vertical section through a third embodiment with atwo-sided journalling of the stator, which is carried by the shaft,

FIG. 4 shows a vertical section through a further embodiment of theinvention, with the generator arranged between two bearings,

FIG. 5 shows a perspective view of an alternative embodiment of anon-rotatable coupling,

FIG. 6 shows a perspective view of an alternative embodiment, with agearbox connected to the turbine shaft, with a generator further beingarranged on a generator support carried by the gear box in the extensionof the, and wherein the torque transmission to the main base is providedby an adapted non-rotatable coupling, and

FIG. 7 shows a perspective view of a further embodiment, with a gearboxconnected to the turbine shaft, and with a generator arranged on agenerator base carried by the gear box over the turbine shaft, andwherein the torque transmission to the main base is provided by anadapted non-rotatable coupling

The invention illustrated in FIG. 1 is based on a coupling of theturbine shaft directly to the generator. It shows a vertical sectionlenghtwise through a shaft bearing according to an embodiment of theinvention. On the top of a tower 1 a horizontal gear rim 2 is attached,which is used for turning of the higher parts of a wind power plantwhich is described in more detail below. Over the gear rim is a rigidbase 4 which serves as a support for the shaft. The base 4 is rotablerelative to the gear rim 2 around its vertical shaft by a suitablebearing. The rotation is activated by a motor 3 arranged at the side ofthe base 4 with a depending shaft with a gear engaging the gear rim 2.

The base 4 provides support for two bearing housings, a front bearinghousing 6 facing the turbine, and a rear bearing housing 7. The bearinghousings together carry the turbine shaft 8, which in turn carries acomplete generator 11. Each bearing housing contains a hearing 9, 10,and is attached to the base 4 with bolts 21.

The generator rotor is carried by a generator shaft 22 which can be acontinuation of the turbine shaft 8. The stator housing 17 is carried bybearings 15, 16 on the shaft 8. Bearings 15, 16 provide an air zap 18which is as constant and small a possible, between the stator 19 and therotor 12, independent of the deflection of the shaft.

The torque from the turbine shaft 8, which through the electric field istransferred to the stator housing 17, is transferred to the base via anon-rotatable coupling 20.

In FIGS. 6 and 7 an alternative embodiment of the invention is shown. Agearbox is arranged between the turbine shaft 8 and the generator 31,both of which mainly correspond to the previous description. The gearbox29, the generator base 30 and the generator 31 all are free to followthe movement of the turbine shaft 8 in the opening between the bearinghousing 7 and its connection to the gearbox 29, except in the directionof the torque. A non-rotatable coupling 33 provides transfer of thetorque from the turbine shaft via the gearbox 29 to the generator 31 andthe main base 4 and limits or totally eliminates damaging forces, whichmay otherwise result in damaging deformations of the gearbox and thegenerator. The non-rotatable coupling 33 comprises a bracket 34 in theform of two arms extending from the main base 4 towards the generator31. The bracket 34 is rigidly attached to the main base and at the freeend connected with a cross yoke 35. Further, at the free end, a kneelink with two linked arms 36, 37 are linked to the end of the bracket oryoke 35 and at a bracket 38 on the side of the gearbox 29. Acorresponding, symmetrically arranged knee link may be provided at theoposite side.

FUNCTION

The function of this arrangement is mainly described by the descriptionand FIG. 1. The weight of and the forces acting on the shaft 8 and thegenerator 11 is carried by the bearings 9, 10 and transferred to thebase 4. The turbine shaft 8 transfers the torque directly to the rotor12 of the generator. The stator housing 17 is carried directly on theturbine shaft. A suitable size of shaft in the vacinity of the generator11 provides sufficient rigidity to ultimately keep a constant and smallair gap 18 between the rotor 12 and the stator 19. A non-rotatablecoupling 20 in the form of an annular dish with a central,circumferential fold increases the pliability in an axial direction,results in transfer of the torque acting on the stator housing 17, dueto the electrical field from the rotor 12, to the base 4 with minimumbending moment.

The non-rotatable coupling 20 is designed and sized to transfer onlytorque from the wind turbine, without deflection of the generator shaft22 due to torque acting on the hub of the wind turbine.

The stator housing 17 thus will follow the movements of the rotor 12 andthe generator shaft 22 and the air gap 18 is maintained mainly constant.

The total structure allows for testing the wind turbine and thegenerator as a complete unit before mounting in situ, and to hoist andmount it to the top of the tower as a readymade unit.

MODIFICATIONS

In FIG. 2 an alternative embodiment is shown, similar parts beingprovided with identical reference numerals as in FIG. 1, and wherein thegenerator shaft 22 is carried by a double journalled bushing 23providing a stator hub, which with another bearing 24 carries the rotor12. The generator shaft 22 has a dish 25 at the free end attached to therotor 12 for transferring torque thereto.

In FIG. 3 a further embodiment based on the same principle is shown. Inthis case a stator dish 17 with a hub is carried by the generator shaft22 with a double bearing, and extendeds into a flange on one side,carrying the active stator parts.

In FIG. 4, in which the same reference numerals as the previous Figuresare used an embodiment is shown, which differs from the embodiments ofFIGS. 1-3 by having the generator arranged between the bearing housings6, 7. The non-rotatable coupling 20 is fastened correspondingly to thebearing housing 6 adjoining the wind turbine.

Generally, the non-rotatable coupling 20 may be fastened to an arbitrarybearing housing, or to the base 4.

In FIG. 5 a further modified embodiment of the base 4 and the bearingunits 6, 7 is shown. In this case the stator 19 is provided with aradial pair of arms 26, extending horizontally at the base 4. The base 4carries a beam 27 which is arranged parallell to the pair of arms 26. Atboth ends, the pair of arms and the beam is connected to a dampingelement 28, which can take torque, but not bending moment and axialforces. The damping elements 28 are provided to take possible momentshock, e g. due to short circuit.

FIGS. 6 and 7 shows usage of the invention wherein a gearbox 29 isarranged between the turbine shaft 8 and generator 31. Other embodimentsof the non-rotatable coupling for transferring of torque from theturbine shaft via gearbox 29 and the generator 31, as long as it isprovided for minimal force transfer between the turbine shaft 8 and thesame elements in all directions except for the torque direction.

1. Wind power plant with a wind turbine with a turbine shaft (8) whichwith a generator shaft (22), which can be an extension of the turbineshaft, is connected to the rotor (12) of all electric generator (11),wherein the rotor (12) is radially surrounded by a stator (19), whereinthe turbine shaft (8) is journalled in two bearing housings (6, 7) withbearings (9, 10) arranged on a base (4) at the top of a tower (1),wherein the base (4) is pivotable around a vertical axis, and wherein amotor (3) is provided to effect the pivoting, characterized in that thegenerator shaft (22) is integrated with or rigidly connected to aflexing turbine shaft (8), that the stator (19) and rotor (12) arecarried by the generator shaft (22), to allow the generator (11) tofollow the flexing movement of the turbine shaft (8), and that thestator (19) is locked against turning by a non-rotatable coupling (20)which transfers substantially no bending moment or axial force actingagainst the flexing of the turbine shaft (8) due to the bending momentacting on the turbine shaft (8) from its hub, the bearings (9 and 10)being provided to allow flexing of the turbine shaft (8).
 2. Wind powerplant according to claim 1, wherein the generator (11) is arranged on aside of the base (4), opposite to the wind turbine or between thebearing housings (6, 7), characterized in that the stator is connectedto a non-rotatable coupling (20) provided to transfer torque andsubstantially no bending moment, preferably an annular dish with acircumferential fold, which connects the stator to a bearing housing. 3.Wind power plant according to claim 1, characterized in that thenon-rotatable coupling (20) is provided for transferring the torque anddampening forces created upon a short circuit of the generator.
 4. Windpower plant according to anyone of the claim 1, characterized in thatthe stator (19) is attached at the generator shaft (22) at one of itsends (FIG. 1) or with a double bearing (FIGS. 2-4) and that the rotor(12) is attached directly to the generator shaft (FIGS. 1, 3, 4) or witha dish to the end of the generator shaft (FIG. 2).
 5. Wind power plantaccording to claim 1, characterized in that the stator (11) is carriedon both sides with side elements (17) non-flexingly supporting thestator (11) non-flexing relative to the generator shaft (22) and theturbine shaft (8) attached to bearings (15, 16) which are carried by thegenerator shaft (FIGS. 1, 4).
 6. Wind power plant according to claim 1,characterized in that the stator (11) is carried at one side by a dishelement (17) non-flexingly supporting the stator relative to thegenerator shaft (22) and the turbine shaft (8) attached to bearings (15,16) which are carried by the generator shaft (FIGS. 2, 3).
 7. Windpourer plant according to claim 1, characterized in that the stator (19)and the base (4) (FIG. 5) are connected by a couple of forcetransferring elements (29) being arranged radially away from thegenerator shaft (22) for transferring torque, e.g. in the form ofelastic damping elements which are arranged between the ends of a pairof arms (26) on the stator and a beam (27) parallel therewith andattached to the base (4) to transfer torque from the stator (19) to thebase (4) without exerting any bending moment or axial tension which mayprevent flexing of the turbine shaft (8) with a bending moment acting onthe shaft from the hub and also dampening forces which can be created byshort circuit in the generator.
 8. Wind power plant according to anyoneof the claim 1, characterized in that the bearings (9 and 10) arespherical.